Virtual biologists observe virtual grasshoppers: an assessment of different mobility parameters for the analysis of movement patterns

An individual-based model was developed to investigate the accuracy of thre e mobility indices commonly used in field studies: mean daily movement, max imal distance and mean activity radius. Although the model is based on a fi eld study of the mobility of the grasshopper Oedipoda germanica (Saltatoria : Acrididae) in Thuringia (Germany), the results are valid more generally. We show that the observational interval is the key factor influencing the a ccuracy of all three indices. Moreover, there is an optimal observational i nterval that minimises the absolute error. The influence of individual mobi lity, recapture probability, accurate registration of the capture and recap ture points and the effect of the observer on the movement of the animals, are also considered. (C) 1999 Elsevier Science B.V. All rights reserved.